Endothelin is an endothelial cell-derived peptide hormone capable of acting on various cells and tissues through its receptors. For example, endothelin is known to cause a rise in intracellular calcium concentration in vascular smooth muscle cells and other cells (Non-Patent Literature 1).
In recent years, it is reported that endothelin promotes a rise in intracellular calcium concentration in epidermal melanocytes (melanin cells) to facilitate cell growth through the intracellular signal transduction system, and to enhance the activity of tyrosinase which is a rate determining enzyme in melanin synthesis (see Non-Patent Literature 2). It is also reported that endothelin is a melanocyte activating factor produced by epidermal keratinocytes (Non-Patent Literature 3) and that endothelin is an important factor in ultraviolet light-induced pigmentation or senile lentigines (Non-Patent Literatures 4 and 5).
Such biological actions of endothelin may well suggest that materials capable of suppressing endothelin action can be useful for reducing or preventing melanin production, pigmentation, or the like.
Whiteworm lichen (scientific name: Thamnolia vermicularis or Thamnolia subuliformis) is a lichen species growing in highlands of China and other areas. Whiteworm lichen is said to be effective in breaking down fat or in dieting, and also in Japan, it is often drunk in the form of tea or the like.